1. Field of the Invention
The present invention relates to metrological rotary devices, such as anemometers and the like. Specifically, the present invention relates to a mechanical coupling for the same, whereby a cup-rotor or other similar low torque device, can be replaced without the use of a tool.
2. Discussion of the State of the Art
There are many coupling devices in use in research and industry that transfer rotational mechanical power. Known devices comprise collets and chucks that can be used to attach various metrological devices. Collets whilst being easy to use suffer from being easily being mounted in a non-preferred axial position. Additionally, the fastening of a collet is dependent upon an operator's judgement to apply a correct amount of torque when locking. A chuck can be quite large and are typically metallic whereby, in use, provide a substantial amount of inertial resistance, too great for many applications, including metrology, especially in wind speed applications.
FIG. 1 shows a prior art system, per GB 1,418,747, a prior art metrological coupling device 1 having a right circular cylindrical chamber with first and a second diameters and a bore, all being concentric with respect to each other, the second diameter being larger than the first diameter. Within the bore, a shaft 2 is a sliding fit, the shaft being operatively positioned therein; the shaft having an annular groove 3 about which the ball can engage, in conjunction with the inside wall of the chamber, about the first diameter, the annular wall of the chamber preventing the relative axial movement of the coupling device with respect to the shaft in one direction and the cap of the coupling device preventing movement in the other axial direction. That is to say, when the ball reaches the position shown by an unbroken line in the drawing further outward movement of the shaft is prevented by the locking action of the ball between the sloping side of the groove and the wall and bottom of the chamber. The shaft is then locked in position in the coupling member and cannot be withdrawn while the coupling remains in the vertical position or thereabouts unless vertical acceleration, vibration or magnetic force is used.
Release of the coupling element is enabled when the ball 4 is within space 6. Upon relative movement of the coupling device away from the shaft, the ball is not obstructed by the annular groove and thereby relative movement between the coupling device and the shaft is not impeded and the components can be separated only when inverted or by the use of strong external magnets. The longitudinal slot 7 in the shaft and engaging pin are used when it is required to prevent relative angular rotation of the two members of the coupling. More than one ball may be present in the chamber.
This prior system, however, suffers from a number of issues, one of which is that the coupling is not balanced about the central axis, which can compromise data when employed in a metrological application.
DE4338278 relates to a device 20 (per FIG. 2) for locking an axially movable securing pin or bolt 22 by the use of a solenoid 23 in a missile environment, where there is an extreme requirement for a high functional reliability. Specifically, this utility model provides a means for locking the axially movable securing pin or bolt by a ball bearing 27 element, which engages in a locking groove 28 on the circumference of the securing bolt by means of a locking ball 27. The solenoid drives a piston 26 via rod 25 within channel 27, the piston being movable so as to enable locking of the shaft 22 by means of the ball bearing. However, this system relates to a remote, electrically controlled arrangement that cannot be utilised in a rotational coupling arrangement.